1. Field of the Invention
The invention relates to a method of detecting and concealing video signal errors, caused by vertically extending film scratches, during television film scanning, in which an error signal is derived at error locations generated by disturbed pixels, and is used in the form of a control signal for concealing errors in the video signal.
Older, frequently used films often show two kinds of errors in the image area: dirt and dust on the surface of the film, and scratches in the running direction of the film, referred to as running scratches, which are caused by mechanical contact between the film-guiding elements and the image area. These errors, appearing as white spots or scratches, are particularly disturbing in electronic scanning and reversal of negative films.
2. Description of the Related Art
German Patent Application P 43 43 095.3 describes a method of concealing dust and scratches in connection with electronic film scanning. By means of temporally adaptive median filtering, film dust and coarse film dirt, as well as scratches accidentally spread across the film image, can be effectively filtered out in so far as they do not occur at the same location in consecutive film frames.